We found large (greater than 10Mum) lipid droplets with bright, vitamin A-specific autofluorescence in the pigment epithelium and other cells of the transition zone ("ora serrata") between the peripheral retina and ciliary epithelium of mice and rats. In order to elucidate the structure and function of these droplets we utilized fluorescence microscopy, histology, and electron microscopy on eyes of animals under various experimental conditions. C57BL/6J mice injected intramuscularly with retinyl acetate in cumulative doses up to 94,000 IU showed increases in the number, size, and fluorescence of lipid droplets in the transition cells of the "ora serrata" region when compared to controls injected with retinoic acid or with the peanut oil solvent alone. Sprague-Dawley rats fed purified diets lacking vitamin A or supplemented with 0.23 to 23.0 mg/kg of retinol showed dose-related changes in the "ora serrata" lipid droplets. These droplets could represent significant storage sites for retinal vitamin A.